Transfer apparatus and method for semiconductor process and semiconductor processing system

ABSTRACT

A transfer apparatus ( 42 ) for a semiconductor processing system includes a transfer member ( 44 ) having a support portion ( 48 ) to place a target substrate (W) thereon, and a drive unit ( 68 ) for driving the transfer member ( 44 ). A reference mark ( 54 ) is disposed adjacent to the support portion ( 48 ). The target substrate (W) has optically observable first and second portions ( 84, 86 ). A storage section ( 63 ) stores a normal image that shows a positional correlation between the reference mark ( 54 ) and the first and second portions ( 84, 86 ), obtained when the target substrate (W) is placed on the support portion ( 48 ) at a normal position. An image pick-up device ( 62 A) takes a detection image that shows a positional correlation between the reference mark ( 54 ) and the first and second portions ( 84, 86 ), when the transfer member ( 44 ) transfers the target substrate (W). An information processing unit ( 62 B) obtains a misalignment amount of the target substrate (W) relative to the normal position, based on the normal image and the detection image.

TECHNICAL FIELD

The present invention relates to a transfer apparatus and method fortransferring a target substrate, such as a semiconductor wafer, in asemiconductor processing system, and also relates to a semiconductorprocessing system. The term “semiconductor process” used herein includesvarious kinds of processes which are performed to manufacture asemiconductor device or a structure having wiring layers, electrodes,and the like to be connected to a semiconductor device, on a targetsubstrate, such as a semiconductor wafer or an LCD substrate, by formingsemiconductor layers, insulating layers, and conductive layers inpredetermined patterns on the target substrate.

BACKGROUND ART

In the process of manufacturing semiconductor integrated circuits (ICs),a semiconductor wafer is subjected to various processes, such as filmformation, oxidation, diffusion, annealing, modification, and etching. Aprocessing system of the so-called cluster tool type, in which processchambers for performing respective processes are connected to a commontransfer chamber, is known as a system for efficiently performing theprocesses described above. In the processing system of the cluster tooltype, wafers are transferred between the process chambers by a transferapparatus disposed in the common transfer chamber.

FIG. 7 is a schematic plan view showing a conventional processing systemof the cluster tool type. As shown in FIG. 7, for example, theprocessing system 2 has a plurality of, e.g., three in this case,process chambers 8A to 8C, which are connected to a common transferchamber 4 that can be vacuum-exhausted, respectively via gate valves 6Ato 6C. The process chambers 8A to 8C are respectively provided withworktables 10A to 10C disposed therein, for placing a semiconductorwafer W on the top surface. Two cassette chambers 14A and 14B areconnected to the common transfer chamber 4 respectively via gate valves12A and 12B, and configured to accommodate a cassette for storingsemiconductor wafers, which are almost circular.

The common transfer chamber 4 is provided with a transfer apparatus 16disposed therein and formed of, e.g., an articulated arm, which isrotatable and extensible/contractible. The transfer apparatus 16 has asupport portion 18 to hold a wafer W, and transfer and deliver itbetween each of the cassette chambers 14A and 14B and each of theprocess chambers 8A to 8C, and between the process chambers 8A to 8C.The common transfer chamber 4 is provided with an orienter 17 providedtherein, for allowing the transfer apparatus 16 to hold a wafer W in theproper direction and at the proper position.

When the transfer apparatus transfers a wafer W, the wafer W is notnecessarily accurately placed at the normal position on the supportportion 18 of the transfer apparatus 16. If a wafer W with amisalignment is placed as it is on the worktable of a next processchamber, the process suffers ill effects. Accordingly, it is necessaryto correct the misalignment of the wafer W, so that the wafer W isplaced on the worktable of the process chamber at the proper position.

A misalignment of a wafer W occurs in the following cases. When the gaspressure in the process chambers 8A to 8C changes, the wafer W may slipon the worktables 10A to 10C. When the wafer W is delivered, the wafermay slip on the worktables 10A to 10C. Where the worktables 10A to 10Care respectively provided with electrostatic chucks, the wafer may bepopped by a residual charge, when a wafer W is delivered from theworktables 10A to 10C. This latter phenomenon occurs, if the change onthe wafer W has not been sufficiently removed when the wafer W isdelivered from the worktables 10A to 10C.

U.S. Pat. No. 5,917,601 (Jpn. Pat. Appln. KOKAI Publication No.10-223732), Jpn. Pat. Appln. KOKAI Publication No. 10-247681, and U.S.Pat. No. 5,483,138 disclose a misalignment detector to solve theproblems described above.

The processing system shown in FIG. 7 also has a conventionalmisalignment detector. Specifically, in the common transfer chamber 4, apair of line sensors 20 and 22 are disposed with a certain distancetherebetween near each of the gate valves 6A to 6C of the processchambers 8A to 8C. When a wafer W passes between the line sensors 20 and22, the wafer W is temporarily stopped, and two positions on the edge(positions on the peripheral contour) thereof are detected. On the basisof these detected values, it is possible to obtain how much misalignmentexists between the center of the wafer and the normal position on thesupport portion 18. The control section of the transfer apparatus 16controls the rotation amount and extension/contraction amount of thetransfer apparatus 16 to offset the obtained misalignment amount, so asto place the wafer W on the worktable at the proper position.

This misalignment detector requires a wafer W in transfer to betemporarily stopped at a position corresponding to the line sensors 20and 22, so as to detect a misalignment amount. For example, thenecessary stop time is about 2 to 3 seconds, depending on theperformance of the line sensors 20 and 22. Accordingly, the wafertransfer cannot be speeded up, thereby lowering the throughput. Thisbrings about a serious problem, particularly where a wafer is subjectedto a number of processes in different process chambers in one processingsystem 2. This is so, because the wafer in transfer has to betemporarily stopped every time when the wafer is transferred into eachof the process chambers, so as to detect a misalignment amount.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a transfer apparatusand transfer method, and a semiconductor processing system, which candetect a misalignment amount of a target substrate without stopping atransfer operation of the target substrate, thereby improving thethroughput.

According to a first aspect of the present invention, there is provideda transfer apparatus for transferring a target substrate, which hasoptically observable first and second portions, in a semiconductorprocessing system, the apparatus comprising:

-   -   a transfer member having a support portion to place the target        substrate thereon;    -   a drive unit configured to drive the transfer member so as to        transfer the target substrate;    -   a reference mark disposed adjacent to the support portion, and        configured to move integratedly with the support portion when        the transfer member transfers the target substrate;    -   a storage section, which stores a normal image that shows a        positional correlation between the reference mark and the first        and second portions, obtained when the target substrate is        placed on the support portion at a normal position;    -   an image pick-up device configured to take a detection image        that shows a positional correlation between the reference mark        and the first and second portions, when the transfer member        transfers the target substrate; and    -   an information processing unit configured to obtain a        misalignment amount of the target substrate relative to the        normal position, based on the normal image and the detection        image.

According to a second aspect of the present invention, there is provideda semiconductor processing system, comprising:

-   -   a plurality of airtight process chambers configured to perform        processes on a target substrate, which has optically observable        first and second portions;    -   an airtight common transfer chamber connected to the plurality        of process chambers respectively via gates; and    -   a transfer apparatus disposed in the transfer chamber to        transfer the target substrate,    -   wherein the transfer apparatus comprises    -   a transfer member having a support portion to place the target        substrate thereon, and being extensible/contractible and        rotatable,    -   a drive unit configured to drive the transfer member so as to        transfer the target substrate,    -   a reference mark disposed adjacent to the support portion, and        configured to move integratedly with the support portion when        the transfer member transfers the target substrate,    -   a storage section, which stores a normal image that shows a        positional correlation between the reference mark and the first        and second portions, obtained when the target substrate is        placed on the support portion at a normal position,    -   an image pick-up device configured to take a detection image        that shows a positional correlation between the reference mark        and the first and second portions, when the transfer member        transfers the target substrate,    -   an information processing unit configured to obtain a        misalignment amount of the target substrate relative to the        normal position, based on the normal image and the detection        image, and    -   a control section configured to control the drive unit so as to        offset a misalignment amount of the target substrate obtained by        the information processing unit, when the transfer member        transfers the target substrate into the process chamber.

According to a third aspect of the present invention, there is provideda transfer method for transferring a target substrate, which hasoptically observable first and second portions, in a semiconductorprocessing system, the method comprising:

-   -   preparing a transfer apparatus, which comprises        -   a transfer member having a support portion to place the            target substrate thereon,        -   a drive unit configured to drive the transfer member so as            to transfer the target substrate, and        -   a reference mark disposed adjacent to the support portion,            and configured to move integratedly with the support portion            when the transfer member transfers the target substrate;    -   storing a normal image that shows a positional correlation        between the reference mark and the first and second portions,        obtained when the target substrate is placed on the support        portion at a normal position;    -   taking a detection image that shows a positional correlation        between the reference mark and the first and second portions,        when the transfer member transfers the target substrate; and    -   obtaining a misalignment amount of the target substrate relative        to the normal position, based on the normal image and the        detection image.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic plan view showing a semiconductor processingsystem of the cluster tool type according to an embodiment of thepresent invention;

FIG. 2 is a block diagram showing the correlation between the transferarm, misalignment detectors, and control section, of a transferapparatus provided in the system shown in FIG. 1;

FIG. 3 is an enlarged sectional view showing the part where the imagepick-up device of a misalignment detector shown in FIG. 2 is installed,along with the transfer arm;

FIG. 4 is a plan view showing a state where a semiconductor wafer havinga notch is placed at the normal position on a support portion of thetransfer apparatus shown in FIG. 2;

FIG. 5 is a view schematically showing a processed image in a coordinatesystem, taken by the image pickup device, in the transfer apparatusshown in FIG. 2;

FIG. 6 is a plan view showing a state where a semiconductor wafer havingan orientation flat is placed at the normal position on a supportportion of the transfer apparatus shown in FIG. 2; and

FIG. 7 is a schematic plan view showing a conventional processing systemof the cluster tool type.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinafter withreference to the accompanying drawings. In the following description,the constituent elements having substantially the same function andarrangement are denoted by the same reference numerals, and a repetitivedescription will be made only when necessary.

FIG. 1 is a schematic plan view showing a semiconductor processingsystem of the cluster tool type according to an embodiment of thepresent invention. As shown in FIG. 1, the processing system 24 has acommon transfer chamber 26, which has an almost regular octagonal shapewith eight ports, and can be vacuum-exhausted. Four of the ports of thecommon transfer chamber 26 are respectively connected to processchambers 30A to 30D via gate valves 28A to 28D. Two of the ports of thecommon transfer chamber 26 are respectively connected to two cassettechambers 38A and 38B via gate valves 36A and 36B. One of the ports ofthe common transfer chamber 26 is connected to a cooling process chamber32, which is open to the inside of the common transfer chamber 26. Theother one of the ports of the common transfer chamber 26 is closed.

Each of the cassette chambers 38A and 38B accommodate a cassette 40,which stores almost circular wafers W. The process chambers 30A to 30Dare respectively provided with worktables 34A to 34D disposed thereinfor holding a target substrate or semiconductor wafer W thereon. Theprocess chambers 30A to 30D are configured to subject a wafer to severalsemiconductor processes selected from the group of, e.g., plasma orthermal CVD, annealing, plasma or plasma-less etching, oxidation,diffusion, and modification.

For example, in this embodiment, the first process chamber 30A is usedfor performing a first CVD process of depositing a first tantalum oxidefilm. The second process chamber 30B is used for performing a firstmodification process of modifying the first tantalum oxide film withultraviolet rays. The third process chamber 30C is used for performing asecond CVD process of depositing a second tantalum oxide film. Thefourth process chamber 30D is used for performing a second modificationprocess of modifying the second tantalum oxide film with ultravioletrays.

The common transfer chamber 26 is provided with an orienter (alignmentmechanism) 60 disposed therein near the cassette chambers 38A and 38B,for performing alignment of a wafer W. The orienter 60 includes a rotarytable 56 for holding and rotating the wafer W, and a line sensor 58 orthe like for detecting positional fluctuations of the peripheral contourof the wafer W. The alignment mechanism 60 may be disposed outside theprocessing system, instead of inside the common transfer chamber.

The common transfer chamber 26 is provided with a transfer apparatus 42disposed therein near the center, and having, e.g., an articulatedtransfer arm 44, which is rotatable and extensible/contractible. FIG. 2is a block diagram showing the correlation between the transfer arm 44,misalignment detectors 62 and 64, and a control section 66. FIG. 3 is anenlarged sectional view showing the part of the transfer apparatus 42where the image pick-up device of the misalignment detector 62 or 64 isinstalled, along with the transfer arm 44. FIG. 4 is a plan view showinga state where a semiconductor wafer having a notch is placed at thenormal position on a support portion of the transfer apparatus 42.

The transfer arm 44 has a first arm portion 45 rotatably disposed on thebottom of the common transfer chamber 26, a second arm portion 46rotatably connected to the distal end of the first arm portion 45, and apick arm portion 47 rotatably connected to the distal end of the secondarm portion 46. The pick arm portion 47 has forks (support portions) 48at the opposite ends, each for placing a wafer W thereon. The transferapparatus 42 holds wafers W on the forks 48, and transfer and deliverthem between one of the cassette chambers 38A and 38B and one of theprocess chambers 30A to 30D and 32, and between the process chambers 30Ato 30D and 32.

As shown in FIGS. 3 and 4, each of the forks 48 has, e.g., four, shortprojections 50 to place and hold a wafer W directly thereon. A stepportion 52 is formed at the proximal portion of each fork 48 to preventa wafer W held thereon from excessively slipping. The proximal portionof each fork 48 is also provided with a reference mark 54 that isoptically observable. The reference mark 54 is of a size large enough tobe recognized by an image pick-up device described later. For example,the reference mark 54 is formed of a hole having a diameter of about 0.1to 0.5 mm and a depth of about 0.5 mm. The reference mark 54 ispositioned on a line that extends through the center of each fork(support portion) 48 and in parallel with a direction in which a wafer Wis transferred when the image pick-up device takes a detection image, asdescribed later.

The misalignment detectors 62 and 64 of the transfer apparatus 42 aredisposed in front of the gate valves 28B and 28D to correspond to theports of the process chambers 30B and 30D, i.e., every other processchamber, in accordance with the order of the process steps. As alsoshown in FIG. 2, the misalignment detectors 62 and 64 have image pick-updevices 62A and 64A, information processing units 62B and 64B, and acommon database 63. The database 63 stores a normal image that shows thepositional correlation between the reference mark 54 and opticallyobservable first and second portions of a wafer W, obtained when thewafer W is placed on a fork (support portion) 48 at the normal position.Each of the image pick-up devices 62A and 64A takes a detection imagethat shows the positional correlation between the reference mark 54 andthe first and second portions of the wafer W, when the transfer arm 44transfers the wafer W.

Each of the information processing units 62B and 64B obtains themisalignment amount of the wafer W relative to the normal position, onthe basis of the normal image and detection image. Each of theinformation processing units 62B and 64B inputs the misalignment amountof the wafer W thus obtained into the control section 66 of the transferapparatus 42, such as a microcomputer. The control section 66 controlsthe drive unit 68 to offset the obtained misalignment amount of thewafer W, when the transfer arm 44 transfers the wafer W into the processchamber. As shown in FIG. 4, in this embodiment, the first and secondportions of the wafer W to be observed are opposite corners of the notch80 of the wafer W. The maximum width of the notch 80 is, e.g., about 1mm.

The misalignment detectors 62 and 64 have completely the samearrangement. Accordingly, only one misalignment detector 62 will beexplained as an example. As also shown in FIG. 3, an observation hole 70having a diameter of about 30 mm is formed in a ceiling plate 26A thatdefines the common transfer chamber 26. The observation hole 70 isprovided with a light transmission window 74 made of a transparentmaterial, such as quartz, which is airtightly attached thereto by asealing member 72, such as an O-ring. The image pick-up device 62A isdisposed above the light transmission window 74, so that it can take animage of the inside of the common transfer chamber 26 through the lighttransmission window 74. The image information taken by the image pick-updevice 62A is sent to the information processing unit 62B through a line76, as described above (see FIG. 2).

The image pick-up device 62A is disposed at a position directly above apath 78 through which each fork 48 moves when the transfer arm 44transfers the wafer W into and from the process chamber 30B. The imagepick-up device 62A is set to be operable at a high speed with which itcan accurately take an image of a fork 48 without stopping the fork 48during transfer of the wafer W. The image pick-up device 62A may beformed of, e.g., a CCD camera, and more specifically an image sensorCV-500 (a trade name; KEYENCE CORPORATION) having a high speed and highaccuracy monitor built therein.

The image pick-up device 62A has a field of view wide enough to take adetection image of one image frame that contains the reference mark 54of a fork 48 and the opposite corners of the notch 80 of the wafer W(see FIG. 4), even where the wafer W is placed on the fork (supportportion) 48 with a considerable misalignment relative to the normalposition. The normal image stored in the database 63 is also formed ofone image frame taken by the image pick-up device that contains thereference mark 54 and the opposite corners of the notch 80 of the waferW. However, each of the detection image and normal image may be formedof a plurality of image frames.

Next, explanation will be given of a process method and transfer methodin the processing system 24 and transfer apparatus 42, with referencealso to FIG. 5.

FIG. 5 is a view schematically showing a processed image in a coordinatesystem, taken by the image pickup device, in the transfer apparatus 42.As described above, this embodiment employs the opposite corners of thenotch 80 of the wafer W (first and second portions) 84 and 86 (see FIG.4) as observation target portions, to recognize the state of the wafer Wplaced on a fork 48. The misalignment amount of the wafer W is detectedby taking an image of the first and second portions and the referencemark 54 of the fork 48.

In FIG. 5, coordinates (x0, y0) denote the position of the referencemark 54. Coordinates (x1, y1) and coordinates (x2, y2) denote positionsof the first and second portions 84 and 86, respectively, obtained whenthe wafer W is placed on the fork (support portion) 48 at the normalposition. Coordinates (x1′, y1′) and coordinates (x2′, y2′) denotepositions of the first and second portions 84 and 86, respectively,obtained when the wafer W is placed on the fork (support portion) 48with a misalignment relative to the normal position.

A semiconductor wafer W is processed in the following order. In thiscase, as explained above, the first to fourth process chambers 30A to30D perform deposition of a first tantalum oxide film, modification ofthe first tantalum oxide film, deposition of a second tantalum oxidefilm, and modification of the second tantalum oxide film, respectively.

At first, the transfer arm 44 is operated to rotate and extend/contractto pick up an unprocessed semiconductor wafer W stored in one, e.g., 38Aof the cassette chambers, through the opened gate valve 36A. Thetransfer arm 44 holds the wafer W on one of the forks 48, transfers itinto the common transfer chamber 26, and rotates to place it on therotary table 56 of the alignment mechanism 60. The alignment mechanism60 rotates the wafer W, and detects its edge by the line sensor 58 todetect the misalignment of wafer W.

Then, when the transfer arm 44 picks up the wafer W by one of the forks48, the transfer arm 44 is controlled to offset the misalignmentdetected by the alignment mechanism 60, so that it can support the waferW on the fork 48 at the normal position. The positional relationship atthis time between the reference mark 54 of the fork 48 and the cornerportions 84 and 86 of the notch 80 of the wafer W takes on a state shownwith the coordinates (x0, y0), (x1, y1), and (x2, y2) in FIG. 5. Thetransfer arm 44 directs this aligned wafer W toward the process chamber30A, which is predetermined. Then, the transfer arm 44 extends totransfer the wafer W into the process chamber 30A through the openedgate valves 28A and places it on the worktable 34A.

Then, the process chamber 30A performs a predetermined process, i.e.,deposition of the first tantalum oxide film, on the wafer W. After thisprocess, the transfer arm 44 extends to insert one of the forks 48 intothe process chamber 30A through the opened gate valves 28A, and supportthe processed wafer W on the fork 48. Then, the transfer arm 44contracts to transfer the wafer W into the common transfer chamber 26.At this time, the wafer W on the fork 48 may have a misalignmentrelative to the normal position.

In order to subject the wafer W to the next process, the transfer arm 44rotates to direct the wafer W toward the next process chamber, e.g.,30B. Then, the transfer arm 44 transfers the wafer W into the processchamber 30B and places it on the worktable 34B, as in the operation oftransferring the wafer W into the process chamber 30A. At this time themisalignment detector 62 detects the misalignment amount of the wafer W.Then, the operation, i.e., the rotational amount andextension/contraction amount, of the transfer arm 44 is controlled tooffset the detected misalignment amount, to place the wafer W on theworktable 34B at the proper position. This offset correction will bedescribed later.

Then, the process chamber 30B performs a predetermined process, i.e.,the first modification process, on the wafer W. After this process, thetransfer arm 44 picks up the wafer W, and transfers it into the commontransfer chamber 26. At this time, the wafer W may be placed on a fork48 again with a misalignment relative to the normal position. Themisalignment detector 62 detects this misalignment amount. When thetransfer arm 44 transfers the wafer W into the process chamber 30C forthe next process, the operation of the transfer arm 44 is controlled tooffset the detected misalignment amount, to place the wafer W on theworktable 34C at the proper position.

Then, the process chamber 30C performs a predetermined process, i.e.,deposition of the second tantalum oxide film, on the wafer W. After thisprocess, the transfer arm 44 picks up the wafer W from the processchamber 30C, and places it on the worktable 34D in the process chamber30D. The operation at this time is the same as that of transferring thewafer W from the process chamber 30A to the process chamber 30B.Specifically, in the course of transferring the wafer W into the processchamber 30D, the misalignment detector 64 detects the misalignmentamount of the wafer W. Then, the operation of the transfer arm 44 iscontrolled to offset the detected misalignment amount, to place thewafer W on the worktable 34C at the proper position.

Then, the process chamber 30D performs a predetermined process, i.e.,the second modification process, on the wafer W. After all the processeson the wafer W are completed, as described above, the processed wafer Wis stored in a cassette in, e.g., the other cassette chamber 38B. Inthis respect, immediately after the second modification process isfinished, the wafer W has a very high temperature. Accordingly, thewafer W is once transferred into the cooling process chamber 32, and iscooled therein, and then is transferred into the cassette chamber 38.

At this time, the processes on the wafer have been completed, the waferW is allowed to have a misalignment on a fork 48 while beingtransferred. However, to increase the transfer accuracy, themisalignment detector 64 detects the misalignment amount of the wafer Wwhen the wafer W is transferred from the fourth process chamber 30D.Then, the wafer W is transferred into the cooling process chamber 32,while offsetting the detected misalignment amount.

As described above, when the wafer W held on the fork 48 is transferredto and from the process chambers 30B and 30D, the misalignment amount ofthe wafer W on a fork 48 is detected. The wafer W passes through aposition directly below each of the image pick-up devices 62A and 64A ofthe misalignment detectors 62 and 64. At this time, each of the imagepick-up devices 62A and 64A takes a detection image that shows thepositional correlation between the reference mark 54 of the transfer arm44 and the first and second portions 84 and 86 of the wafer W. Each ofthe information processing units 62B and 64B compares the detectionimage with the normal image stored in the database 63 by means ofimage-processing, to obtain the misalignment of the wafer W on the fork(support portion) 48 relative to the normal position.

In FIG. 5, the positions of the reference mark 54 and the first andsecond portions 84 and 86 of the wafer W in the normal image areindicated with the coordinates (x0, y0), coordinates (x1, y1), andcoordinates (x2, y2), respectively. On the other hand, when the wafer Wis placed on the fork 48 with a misalignment relative to the normalposition, the positions of the first and second portions 84 and 86 areindicated with the coordinates (x1′, y1′) and coordinates (x2′, y2′),respectively. Each of the information processing units 62B and 64Bperforms image processing such that the reference mark 54 in the normalimage coincides with the reference mark 54 in the detection image,thereby obtaining the misalignment of the detection image relative tothe normal image. Then, it calculates the misalignment amount Δt1 of thecoordinates (x1′, y1′) of the detection image relative to thecoordinates (x1, y1) of the normal image, and the misalignment amountΔt2 of the coordinates (x2′, y2′) of the detection image relative to thecoordinates (x2, y2) of the normal image. The control section 66controls the operation, i.e., the rotational amount andextension/contraction amount, of the transfer arm 44 to offset themisalignment amounts Δt1 and Δt2, to place the wafer W on the worktableat the proper position.

As described above, with transfer method according to the embodiment ofthe present invention, the misalignment amount of a wafer W on the fork48 is detected without stopping the transfer operation of the wafer W.As a consequence, the wafer transfer operation can be performed swiftly,thereby improving the throughput of wafer processing.

In the semiconductor processing system shown in FIG. 1, the processchambers perform deposition and modification. Processes to be performedin the process chambers are not limited to specific ones. In the systemshown in FIG. 1, the two misalignment detectors 62 and 64 are disposedat every other process chamber, in order to improve wafer transferefficiency. However, only one misalignment detector may be used in thesystem. In this case, if a wafer W may be placed on a fork (supportportion) 48 with a misalignment relative to the normal position, thewafer W is caused to pass below the image pick-up device of thismisalignment detector, thereby detecting the misalignment amount. In thesystem shown in FIG. 1, the pick arm portion 47 of the transfer arm 44has two forks 48, but it may be designed to have only one fork 48.

In the system shown in FIG. 1, a wafer W having a notch 80 is handled asa target substrate, but a wafer having an orientation flat may behandled as a target substrate. FIG. 6 is a plan view showing a statewhere a semiconductor wafer having an orientation flat 90 is placed atthe normal position on a support portion of the transfer apparatus 42shown in FIG. 2. In this case, corner portions 92 and 94 at the oppositeends of the linear orientation flat 90 function as observation targetportions. In general, the length of the orientation flat 90 is about 60to 70 mm, which is far lager than that of the notch 80. Accordingly, animage pick-up device used in this case preferably has a large field ofview. A semiconductor wafer to be handled is not limited to a specificsize, but any one of, e.g., 6-inch, 8-inch, and 12-inch wafers may behandled as a target substrate. Furthermore, in place of a semiconductorwafer, another substrate, such as an LCD substrate or glass substrate,may be handled as a target substrate.

The present invention is not limited to the embodiments described above,but can be practiced in various manners without departing from thespirit and scope of the invention. The features of the embodimentsdescribed above can be arbitrarily combined with each other in practice,thereby obtaining combined effects.

1. A transfer apparatus for transferring a target substrate, which hasoptically observable first and second portions, in a semiconductorprocessing system, the apparatus comprising: a transfer member having asupport portion to place the target substrate thereon; a drive unitconfigured to drive the transfer member so as to transfer the targetsubstrate; a reference mark disposed adjacent to the support portion,and configured to move integratedly with the support portion when thetransfer member transfers the target substrate; a storage section, whichstores a normal image that shows a positional correlation between thereference mark and the first and second portions, obtained when thetarget substrate is placed on the support portion at a normal position;an image pick-up device configured to take a detection image that showsa positional correlation between the reference mark and the first andsecond portions, when the transfer member transfers the targetsubstrate; and an information processing unit configured to obtain amisalignment amount of the target substrate relative to the normalposition, based on the normal image and the detection image.
 2. Theapparatus according to claim 1, wherein the image pick-up device isconfigured to take the detection image while the transfer member ismoving along with the target substrate placed thereon.
 3. The apparatusaccording to claim 1, wherein the reference mark is disposed on aproximal portion of the transfer member, which supports the supportportion.
 4. The apparatus according to claim 3, wherein the referencemark is positioned on a line that extends through a center of thesupport portion and in parallel with a direction in which the targetsubstrate is transferred when the detection image is taken.
 5. Theapparatus according to claim 1, wherein the first and second portionscomprise corner portions formed at an edge of the target substrate. 6.The apparatus according to claim 1, wherein the reference mark and thefirst and second portions in the normal image are positioned in oneimage frame taken by the image pick-up device.
 7. The apparatusaccording to claim 1, wherein the transfer member isextensible/contractible and rotatable.
 8. The apparatus according toclaim 7, further comprises a control section configured to control thedrive unit so as to offset a misalignment amount of the target substrateobtained by the information processing unit, when the transfer membertransfers the target substrate.
 9. A semiconductor processing system,comprising: a plurality of airtight process chambers configured toperform processes on a target substrate, which has optically observablefirst and second portions; an airtight common transfer chamber connectedto the plurality of process chambers respectively via gates; and atransfer apparatus disposed in the transfer chamber to transfer thetarget substrate, wherein the transfer apparatus comprises a transfermember having a support portion to place the target substrate thereon,and being extensible/contractible and rotatable, a drive unit configuredto drive the transfer member so as to transfer the target substrate, areference mark disposed adjacent to the support portion, and configuredto move integratedly with the support portion when the transfer membertransfers the target substrate, a storage section, which stores a normalimage that shows a positional correlation between the reference mark andthe first and second portions, obtained when the target substrate isplaced on the support portion at a normal position, an image pick-updevice configured to take a detection image that shows a positionalcorrelation between the reference mark and the first and secondportions, when the transfer member transfers the target substrate, aninformation processing unit configured to obtain a misalignment amountof the target substrate relative to the normal position, based on thenormal image and the detection image, and a control section configuredto control the drive unit so as to offset a misalignment amount of thetarget substrate obtained by the information processing unit, when thetransfer member transfers the target substrate into the process chamber.10. The system according to claim 9, wherein the image pick-up device isdisposed outside the common transfer chamber, and a light transmissionwindow is formed on the common transfer chamber to correspond to theimage pick-up device.
 11. The system according to claim 9, wherein theimage pick-up device is disposed in front of one of the gates providedat the plurality of process chambers.
 12. The system according to claim11, wherein the image pick-up device is one of a plurality of imagepick-up devices equivalent to each other, and the plurality of imagepick-up devices are disposed in front of some of the gates provided atthe plurality of process chambers.
 13. The system according to claim 12,wherein the number of the plurality of image pick-up devices is smallerthan the number of the plurality of process chambers.
 14. The systemaccording to claim 9, wherein the image pick-up device is configured totake the detection image while the transfer member is moving along withthe target substrate placed thereon.
 15. The system according to claim9, wherein the reference mark is disposed on a proximal portion of thetransfer member, which supports the support portion.
 16. The systemaccording to claim 15, wherein the reference mark is positioned on aline that extends through a center of the support portion and inparallel with a direction in which the target substrate is transferredwhen the detection image is taken.
 17. The system according to claim 9,wherein the first and second portions comprise corner portions formed atan edge of the target substrate.
 18. The system according to claim 9,wherein the reference mark and the first and second portions in thenormal image are positioned in one image frame taken by the imagepick-up device.
 19. A transfer method for transferring a targetsubstrate, which has optically observable first and second portions, ina semiconductor processing system, the method comprising: preparing atransfer apparatus, which comprises a transfer member having a supportportion to place the target substrate thereon, a drive unit configuredto drive the transfer member so as to transfer the target substrate, anda reference mark disposed adjacent to the support portion, andconfigured to move integratedly with the support portion when thetransfer member transfers the target substrate; storing a normal imagethat shows a positional correlation between the reference mark and thefirst and second portions, obtained when the target substrate is placedon the support portion at a normal position; taking a detection imagethat shows a positional correlation between the reference mark and thefirst and second portions, when the transfer member transfers the targetsubstrate; and obtaining a misalignment amount of the target substraterelative to the normal position, based on the normal image and thedetection image.
 20. The method according to claim 19, wherein thetransfer member is extensible/contractible and rotatable, and the methodfurther comprises transferring the target substrate by the transfermember, while controlling the drive unit to offset the obtainedmisalignment amount of the target substrate.